Summary

Python 3.10 generates __match_args__ on named tuples so their fields can be used in positional class patterns. We already synthesize other generated named-tuple attributes, but did not expose __match_args__.

from typing import NamedTuple

class Point(NamedTuple):
    x: int
    y: str

reveal_type(Point.__match_args__)  # tuple[Literal["x"], Literal["y"]]

The gradual fallback for named tuples with unknown fields comes from NamedTupleFallback, as proposed in python/typeshed#15906. (I've included a temporary copy of that typeshed change until approved.)